This invention relates to an image signal processing apparatus for displaying an image. More particularly, the invention relates to a signal processing apparatus for displaying signals from two signal sources on each of two display units.
When video information is displayed on a display device such as a liquid-crystal display (referred to as an xe2x80x9cLCD xe2x80x9d hereinafter), it is necessary to prevent a residual image caused by DC components in the video signal. In the prior art, this is accomplished by using a method in which the polarity of the video signal is reversed at fixed periods.
Further, head-mounted displays worn by an observer have been proposed in which two LCDs are used and video information for the left and right eyes of the observer is displayed on respective ones of the LCDs. When two LCDs are used, however, it is necessary that the video signal be reversed in polarity on each signal path at fixed periods. One conventional method of achieving this is to provide each signal path with signal processing means for polarity reversal and signal processing means for no reversal of polarity and switch between the two means in each signal path. Another method is to provide each signal path with one signal processing means capable of switching between reversed/non-reversed polarity, and switch the polarity of the signal processing means per se to thereby change over the polarity of the video signal.
However, with the method of providing the signal processing means for reversal and non-reversal in the prior art described above, there are too many signal processing means. And with the method of providing the signal processing means that can be switched between reversal/non-reversal and changing over the polarity of this signal processing means, it is necessary to adjust the amount of delay, between reversal time and non-reversal time in each signal processing means.
Further, methods of displaying a three-dimensional image on a display unit have been proposed in the prior art. According to one method, video signals representing left- and right-eye images of an object, in which the images differ by an amount corresponding to parallax between the two eyes of the observer, are fed into a display unit such as CRT so as to alternate between the left eye image field and the right eye image field of the object. The observer wears a device such as glasses having a shutter function. By opening and closing the shutters in sync with the changeover between the video signals for the left and right eyes, the image for the left eye is sent to the left eye and the image for the right eye is sent to the right eye, whereby three-dimensional vision is obtained.
With this example of the prior art, however, a circuit is required for switching between the two video signals every field in order to obtain three-dimensional vision. In addition, the glasses having the shutter function must be worn and the shutter must be opened and closed in sync with the images. Furthermore, even if this approach is adopted, flicker is produced since the image seen by only one eye occurs every other field.
An object of the present invention is to provide means through which the number of signal processing means can be reduced as well as the number of adjustments of delay time between reversal and non-reversal of video-signal polarity.
Another object of the present invention is to provide a signal processing apparatus provided with two video-signal input terminals, two signal processing means and two display means one of which can be seen only by the right eye and the other of which can be seen only by the left eye, the video signal for the right eye is sent to the display means for the right eye and the video signal for the left eye is sent to the display means for the left eye, whereby a two-dimensional image or a three-dimensional image can be displayed without producing flicker.
A further object of the present invention is to provide a signal processing apparatus in which a pair of parallax image signals for both eyes, signals which are respective images having a wide angle of view in the horizontal direction and identical image signals are sent to first and second video-signal input terminals, whereby a three-dimensional image, a panoramic image and identical images, respectively, are obtained.
Yet another object of the present invention is to provide a signal processing apparatus having the minimum amount of circuitry, the apparatus being provided with means for synchronizing video signals which have entered from two video-signal input terminals, whereby two signal processing means may be consolidated as a single shared signal processing means and two drive circuits may be consolidated as a single shared drive circuit.
A further object of the invention is to provide a signal processing apparatus in which video signals which have entered from two video-signal input terminals are selectively switched between video signals and displayed on two display means in a first or second display mode, whereby a two-dimensional image or a three-dimensional image is displayed without producing flicker, and in which the same two-dimensional image is displayed on the two display means in a third or fourth display mode.
A further object of the present invention is to provide a signal processing apparatus provided with two detecting means for detecting the absence or presence of video signals inputted from two video-signal input means, in which switching between a two-dimensional image display and a three-dimensional image display is performed automatically depending upon whether or not video signals are being applied to the two video-signal input terminals.
Still another object of the present invention is to provide a signal processing apparatus in which, when a two-dimensional image is displayed in the third mode or fourth mode, consumed current at the time of use is reduced by employing either of the two signal processing means.
Still another object of the present invention is to provide a signal processing apparatus in which, in a case where video signals enter from two video-signal input terminals, video signals supplied to the left and right display means are switched between selectively, whereby it is possible to prevent the video signals from being supplied to the left-eye and right-eye display means erroneously and displayed on the wrong sides.
According to the present invention, the foregoing objects are attained by providing a signal processing apparatus comprising reversing means for reversing polarity of a video signal, and mode selecting and executing means. for alternately selecting and then executing a first mode and a second mode at a prescribed time interval, wherein the first mode is for displaying a first video signal on first display means and inputting a second video signal to the reversing means to reverse the polarity of the second video signal and then display the second video signal on second display means, and the second mode is for inputting the first video signal to the reversing means to reverse the polarity of the first video signal and then display the first video signal on the first display means, and displaying the second video signal on the second display means.
Further, according to the present invention, the foregoing objects are attained by providing a signal processing apparatus comprising first and second signal processing means for respectively converting a first video signal and a second video signal into first and second converted video signals, of a prescribed format, capable of being displayed, first display means for displaying the first converted video signal at a position capable of being seen solely by an observer""s right eye, and second display means for displaying the second converted video signal at a position capable of being seen solely by the observer""s left eye.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designated the same or similar parts throughout the figures thereof.